1. The Field of the Invention
This invention is concerned with the art of providing roadway and other traffic carrying surfaces with traffic regulating signs, such as traffic lane dividing lines and the like and, more particularly, is concerned with means for improving the anti-skid properties and/or the nighttime visibility of the marked area of the road surface.
2. The Prior Art
The art of providing roadway pavements with traffic regulating signs is a well worked one and extensive comments about it are unnecessary. Generally, such signs can be provided by painting or otherwise forming the sign on the roadway pavement, or by applying and adhesively securing on said pavement strips or tape materials. In any case a neatly defined and clearly visible sign has a smooth and compact outer surface which is not receptive to nor retentive of dirt, greasy particles and tiny rubbery particles detached from vehicles' tires, so that the sign will maintain its nearly pure white or clear color. Several compositions are well known for providing suitable and wear resistant signs on traffic carrying surfaces.
It is further known that the thus formed smooth marked areas are undesirably skiddish. Further, the visibility of the markings is undesirably low at nighttime when substantially one source of light only is provided by a vehicle's headlamps, expecially in rainy weather, when a film or thin layer of water exists on the road pavement and forms a mirror-like surface thereon.
Various means have been heretofore proposed for at least partially avoiding the undesirable characteristics of the conventionally formed signs. In the prior U.S. Pat. No. 3,587,415 it has been proposed to provide on the smooth highly visible marking area a plurality of spaced plates or reliefs having coarse upper faces to improve the overall anti-skid character of the sign. Such plates are formed of aggregates including resin bonded retroreflective glass beads for improving also the nighttime visibility of the sign.
In my prior U.S. Pat. No. 3,746,425 there has been described a manner for providing aggregates of the above character which include an exceedingly high multiplicity of glass beads for correspondingly increasing the number of the "light spots" contributing to a better nighttime visibility.
With a view towards improving the anti-skid properties of the marked areas, for a substantial contribution to traffic safety, my Canadian Pat. No. 929,696 (U.S. patent application Ser. No. 153,218, filed June 15, 1971, now U.S. Pat. No. 3,782,843) proposes to add to and partially embed in the marking composition a multiplicity of very hard crystals, such as of corundum, to provide on the marked area a multiplicity of hard, sharp and upwardly projecting points adapted to frictionally engage the tire treads and to prevent skidding even if the vehicle is engaged in speeding around a curve or in an emergency braking action.
Reference is hereby made to the disclosures of the above patent literature as to the various compositions, binders, fillers, retroreflective beads, crystalline particles and other substances which, individually considered, can be made use of for carrying out the present invention and which, therefore, will not be described and specified in detail as this description proceeds.